The embodiments described herein relate generally to a gas dehydration system and, more particularly, to a sub-system within a gas dehydration system in which water is removed from a solvent.
At least some known integrated gasification combined cycle (IGCC) systems produce carbon dioxide (CO2) while producing synthesis gas, or “syngas.” The CO2 produced by the IGCC system can be captured to reduce emissions from the IGCC system. In known IGCC systems, the captured CO2 is typically compressed and dehydrated to meet downstream specifications. A key specification value is the water content of the captured CO2.
Dehydration of natural gas from reservoirs has been performed during gas processing using, for example, triethylene glycol (TEG) or diethylene glycol (DEG), as a solvent. In such systems, the solvent must be dehydrated prior to being re-used in the natural gas dehydration system because the water-laden solvent does not efficiently remove water from the natural gas. As the purity of a solvent increases, the dehydration capacity of the solvent also increases. As used herein, the term “purity,” as it relates to a solvent, refers to an amount of water in the solvent and/or a concentration of the solvent by percent (%) weight. As the purity of the solvent increases, the water concentration of the solvent decreases. Conversely, as the purity of the solvent decreases, the water concentration of the solvent increases.
In at least one known CO2 dehydration system in an IGCC system, dried CO2 is channeled from a gas exit knock-out drum into a Stahl column (gas stripping column) to dry a solvent. A dried solvent produced using the dry CO2 is usually greater than about 99.0% pure. However, the dry CO2 is a valuable product stream, and using the dry CO2 to dry the solvent may reduce the percentage capture of the CO2 dehydration system.